What has happened was that in the past, the dc spilled something on the table. They wiped the spill on top of the mat but neglected to wipe underneath. Some have mildew stains. I have attempted to soak them in bleach but to no avail. I could try again using a stronger solution..

any ideas...I am thinking of switching to cloth placemats to avoid this problem in the future.

I am going to try this on an area of caulk on the tub. It is the one area that grows black mold. I have tried several products, but maybe I should take preventive measures and spray it every morning after all showers. I think, though I'll start with vinegar. My husband recently replaced the caulk, again. While it's on my mind, I should do it. Let me know if it works on the placemats.